Question

The mass of a hot-air balloon and its occupants is 500 kg
(excluding the hot air inside the balloon). The air outside the
balloon has a pressure of 1.01 105 Pa and a density of 1.29 kg/m3.
To lift off, the air inside the balloon is heated. The volume of
the heated balloon is 560 m3. The pressure of the heated air
remains the same as the pressure of the outside air. To what
temperature (in Kelvins) must the air be heated so that the balloon
just lifts off? The molecular mass of air is 29 u.
K